Marquez is suspected of purchasing the two "assault-style" rifles over three years ago. Authorities haven't been able to talk to him because he checked himself into a mental hospital after the attack, a law enforcement official told The Associated Press.

Authorities with guns drawn raided Marquez's home in Riverside early Saturday, breaking windows and using a cutting torch to get into the garage, neighbors said.

Witnesses also saw authorities leaving with a box and a bag Sunday morning. Residents in the neighborhood where Marquez and Farook used to live said the pair seemed to be good friends for several years.

In Riverside, neighbors said Marquez lives in the home with his mother, stepdad and other siblings and that he mostly kept to himself.

Authorities said the rifles were purchased legally in 2011 and 2012, but it is unclear how the weapons came into Farook's possession. On Friday, FBI Director James Comey said the gun purchaser was "not a suspect, at least at this point."

Farook and his wife Tashfeen Malik used the two rifles, along with two handguns that the couple purchased, to kill 14 people at the Inland Regional Center during a holiday party.

The two were later killed in a gun battle between police about a mile away from the center.